Google's celebration of the 30th anniversary of Pac-Man last week flooded Mozilla's Firefox support forum with complaints about siren sounds and offbeat music.

Others asked security vendors if they'd been infected with a virus.

On Friday, Google posted a JavaScript-based version of Pac-Man on its main search page as an homage to the 1980 video game, the latest example of what the company terms "doodles," which are usually static images that celebrate "on this day" events.

But the game freaked out some Firefox users, said James Socol, a Web development engineer at Mozilla.

"Unfortunately, in the initial release [of the game], [the Pac-Man] sounds started playing automatically -- an oversight or an homage to , I guess," said Socol on his blog today. "Even if Google was open in a background tab or window, or in a hidden iframe created by an add-on, the Pac Man music and sound effects would start. And that confused some people."

So many, in fact, heard the sounds that when they didn't find an explanation on Mozilla's support site , they posted enough questions on the support forum to slow the company's database server to a crawl.

"The pounding we took on the forums also caused replication on our slave databases to fall behind by as much as 1.25 hours, so even when we wrote an article about the noises, it didn't show up for most people," Socal added.

"We just got DDOSed by Pac-Man," Socal said another Mozilla engineer quipped, referring to a distributed denial-of-service attack, the malicious assaults that attempt to bring down a Web site.

Several Firefox users reported that they were able to eliminate the background sounds by disabling or removing the CoolPreviews add-on, which lets users preview links and media content without abandoning the active page.

Other users spooked by the background sounds wondered whether they had been nailed by malware.

"We had a new kind of 'virus' attack today that people were calling in about," said Mike Williams, a support manager with Clearwater, Fla.-based Sunbelt Software. "A few people, including an admin[istrator], called in thinking they had virus with the sound of a siren in the background of their Web browser."

Google has removed the Pac-Man doodle from its home page and placed it on a peripheral part of its site . Automatic game sounds have since been disabled; they now begin to play only after the user clicks on the "Insert Coin" button.

Pac-Man was first released on May 22, 1980, by Japanese company Namco, and appeared in the U.S. later that year on arcade machines made by Midway.